This will probably be a species only tank so how many should I have, I'm thinking 10? (I don't like crowded tanks)
I'm sure I'll end up with snails in there but I assume ghost shrimp would be fine too?
Just how densely planted should I have it?
I see they like subdued lighting, I have a crappy incandescent light thing from a smaller tank that I could use but I'm not sure how good of an idea it'll be for the plants where I could just get floating plants with good lights...

If it was me I would go with HOB filter the underwater one will take room up in your tank. thats just my opinion. Do you have a tank that is already running that you could seed your new tank with. I would go with about 8 fish they get about 1.5 in also they are delicate and really prefer a already established tank. A tank thats about 3 to 6 months old. Lights if you have the kind that takes screw in light bulbs you could go with the spiral 65ook screw in bulbs if you added 2 26wt that would give you enough for low light plants and moss I have high light plants so I have 4 on my 20 gal long. you can check out my tanks in my profile. Hope this helps Pat

To restrict water movement for these fish, I would suggest an internal sponge or foam type filter with the outflow directed against the end glass where the filter is placed. The Fluval linked will work for this.

In a 20g long, a group of 7 Trichopsis pumila will work, with lots of plants including thick floating vegetation. The males are territorial when they are protecting a nest, and in a good environment spawning will be continual. I've had to move my group of 5 (2 males, 3 females) from tank to tank due to their pestering of other fish including those larger than themselves.

I agree that incandescent lighting works well over these sized tanks, and the compact fluorescent bulbs in a daylight (6500K) will provide good light for plants. The floating plants will dim the light for the fish.

The aquarist is one who must learn the ways of the biologist, the chemist, and the veterinarian.[unknown source]

Something we all need to remember: The fish you've acquired was quite happy not being owned by you, minding its own business. If you’re going to take it under your wing then you’re responsible for it. Every aspect of its life is under your control, from water quality and temperature to swimming space. [Nathan Hill in PFK]